首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   223868篇
  免费   6887篇
  国内免费   539篇
耳鼻咽喉   3025篇
儿科学   8537篇
妇产科学   6746篇
基础医学   29544篇
口腔科学   6252篇
临床医学   18968篇
内科学   40859篇
皮肤病学   5369篇
神经病学   14870篇
特种医学   11343篇
外国民族医学   101篇
外科学   32212篇
综合类   1303篇
一般理论   9篇
预防医学   19076篇
眼科学   4746篇
药学   15510篇
  2篇
中国医学   171篇
肿瘤学   12651篇
  2021年   900篇
  2019年   1048篇
  2018年   4609篇
  2017年   4739篇
  2016年   4135篇
  2015年   5788篇
  2014年   5367篇
  2013年   4952篇
  2012年   11825篇
  2011年   6672篇
  2010年   3398篇
  2009年   4875篇
  2008年   3779篇
  2007年   4471篇
  2006年   4621篇
  2005年   12652篇
  2004年   14057篇
  2003年   9495篇
  2002年   4708篇
  2001年   4877篇
  2000年   2268篇
  1999年   6308篇
  1992年   7027篇
  1991年   7246篇
  1990年   7499篇
  1989年   7081篇
  1988年   6589篇
  1987年   6338篇
  1986年   6074篇
  1985年   5358篇
  1984年   3706篇
  1983年   3010篇
  1982年   1097篇
  1981年   865篇
  1980年   901篇
  1979年   3920篇
  1978年   2432篇
  1977年   1865篇
  1976年   1641篇
  1975年   2546篇
  1974年   3198篇
  1973年   2815篇
  1972年   2828篇
  1971年   2803篇
  1970年   2614篇
  1969年   2538篇
  1968年   2302篇
  1967年   2209篇
  1966年   1938篇
  1965年   1174篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
INTRODUCTION: Transesophageal echocardiography (TEE) has become increasingly useful in the study of patients with suspected pulmonary thromboembolism. OBJECTIVE: The aim of this study was to prospectively evaluate the usefulness of TEE in the study of the distal part of the left pulmonary artery (LPA) as well as the influence of this procedure on total echocardiographic exam duration. METHODOLOGY: A prospective study in two groups of consecutive patients referred for TEE with a one- year interval between evaluation of Group A: 33 patients, 17 male, mean age 54 +/- 24 years, and Group B: 42 patients, 20 male, mean age 48 +/- 27 years (p = NS). The procedure was considered long when it took more than 3 min to evaluate the distal part of the LPA. RESULTS: In group A we were able to visualize the distal part of the LPA in 24 patients (73%) without significant prolongation of total exam duration in 16 patients (48% of group A). In one of the patients with suspected pulmonary thromboembolism thrombi were only observed in the distal part of the LPA. In group B we were able to visualize the distal part of the LPA in 36 patients (86%) without significant prolongation of total exam duration in 26 patients (61% of group B). CONCLUSIONS: 1. Visualization of the distal part of the LPA was possible in more patients, and with TEE time prolongation in less patients, in group B. These differences can be accounted for by the training of the operator in this technique. 2. The importance of visualization of this part of the LPA in guiding treatment in the subset of patients with pulmonary thromboembolism confirms the usefulness of this specific procedure.  相似文献   
83.
The frequency and pathophysiology of freezing of gait (FoG) in atypical parkinsonism is unknown. We analysed the frequency of FoG in postmortem-confirmed atypical parkinsonian disorders (APD) comprising corticobasal degeneration (CBD), dementia with Lewy bodies (DLB), multiple system atrophy (MSA), and progressive supranuclear palsy (PSP). Sixty-six patients with pathologically confirmed APD (CBD, n = 13; DLB, n = 14; MSA, n = 15; PSP, n = 24) formed the basis for a multicenter clinicopathological study. Clinical features at first and last clinical visit were abstracted from patient records on standardized forms following strict instructions. At the first visit (median 36 months after symptom onset), 24% of APD had FoG (CBD, 8%; DLB, 21%; PSP, 25%; MSA, 40%). Logistic regression analysis showed a significant association of FoG and urinary incontinence (P = 0.04) at first visit. At last visit, 47% of APD had FoG (CBD, 25%; PSP, 53%; DLB, 54%; MSA, 54%). Clinicopathological correlation based on routine postmortem examination failed to identify a consistent neuropathological substrate of FoG. This study demonstrates that (1) FoG is common in APD, and (2) urinary incontinence is significantly associated with FoG in these disorders. Whether FoG and urinary incontinence share similar neuropathological substrates remains to be determined by future studies.  相似文献   
84.
85.
86.
An epidemiologic study of coeliac disease in a geographically defined area of Sweden showed that the prevalence was 95.5/10(5) inhabitants aged 15 years or more. The highest prevalence, 178/10(5) inhabitants, was found in the age group 65-74 years. The lowest prevalence, 39/10(5) inhabitants, was found in patients aged 15-24 years. Among the associated diseases an especially high incidence of associated thyroid disease was observed: thyrotoxicosis occurred in 5.0% and hypothyroidism in 5.8% of the patients.  相似文献   
87.
88.
The splenic arteriovenous differences in plasma amino acid concentrations were assessed in situ by peroperative sampling in 11 patients undergoing splenectomy because of benign and malignant hematologic diseases. The total difference was about 250 mumol/l, which suggests that the spleen contributes about 11 mumol/100 g spleen/min of amino acids to the portal vein. This means that the liver extraction of amino acids may be at least 10% greater than previously believed.  相似文献   
89.
In a randomised, double-blind study, 20 women with idiopathic detrusor instability and associated symptoms were treated with terodiline 25 mg bd, placebo, and emepronium bromide 200 mg tds--each drug being given for 3 weeks with placebo as wash-out period before cross-over. The results were evaluated according to drug preference, frequency charts and elimination of detrusor instability on cystometry. Serum levels of both drugs were monitored as control of tablet intake. The preference for terodiline to placebo was statistically significant: 14/3 women (P less than 0.05), and the majority of women (12/4) preferred terodiline to emepronium. Terodiline also gave a small but significant reduction in 24 h micturition frequency and eliminated detrusor instability in almost 50% of the patients (P less than 0.05). Side effects were frequent but mild in all three treatment periods. It was concluded that terodiline offers an alternative in the treatment of female detrusor instability.  相似文献   
90.
The influence of the pore size of Nucleopore diffusion-chamber filters on the rate of proliferation and differentiation of periosteal cells in muscle was studied in 44 growing rabbits. Periosteal grafts were placed in chambers (16-19 in each experimental group) sealed with filters with a pore size of 0.4, 0.6, 0.8, 1.0, or 2.0 micron. Each chamber was implanted into the paraspinal muscle of the rabbit, where it remained for 16 weeks. The osteochondrogenic activity of the graft grew linearly when the pore size increased from 0.4 to 1.0 micron. In the chambers with a pore size of 2.0 micron, both bone and cartilage were found in only one chamber. Bone and cartilage were not found outside any of the chambers. The present results showed that the pore size of the filters significantly affected the ability of the periosteal graft to form bone and cartilage.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号